The invention relates to a method for separating condensable substances from gases or gas mixtures. In particular for the separation of water from air, with the use of porous materials.
Many parts of the earth, especially arid regions such as the Sahelian zone or numerous torrid deserts located at a considerable distance from the sea, lack reserves of drinking water. Besides transporting drinking water, the only other possibility is to obtain it from moist air. Known in this connection is the direct condensation of air below the dew point and the adsorption of water from zeolites, active charcoal or silica gels, see for example DE-PS 2660 068. Water stored in this manner is extracted from the material by warming and then condensed.
The known methods are not particularly effective in terms of the actual yield of water since the regeneration of the moisture absorbed by the material must overcome high bonding energies or is solely oriented to a daily absorbent filling (see DE 44 30 901 C1 and EP 0003064 A1). Here adsorption occurs mostly at night and desorption by day, with the air being heated directly by resorting to solar collectors or indirectly with the use of heat accumulators. The recovery of water is then conducted by day (EP 0003 964 A1) or at night using a cascade connection (DE 4430901 C1). A further known method for the expenditure of energy in the regeneration of adsorbents is the utilization of electric energy using wall grids or electrodes (DE 196 13 326 A1).
The Method of capillary condensation, long known from the relevant literature (BRUNAUER, Stephen. et. al.: Some Remarks about Capillary Condensation and Pore Structure Analysis. In: Journal of Colloid and Interface Science. Vol. 25, p. 353-358: KADLEC, O., DUBININ: M.M.: Comments on the Limits of Applicability of the Mechanism of Capillary Condensation. In: Journal of Colloid and Interface Science, Vol. 31. No. 4. Dec. 1969, p. 479-489) has so far only been employed for the extraction of solvents from gas (DE 2843416 A1. DE 196 13326 A1) without taking into account its existing potential for improved desorption.